Open AccessInterplanetary magnetic field control of polar patch velocity
Author(s) -
Zhang Y.,
McEwen D. J.,
Cogger L. L.
Publication year - 2003
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2002ja009742
Subject(s) - physics , interplanetary magnetic field , solar wind , azimuth , magnetosphere , polar , ionosphere , convection , drift velocity , geodesy , stochastic drift , magnetic field , geophysics , computational physics , electric field , meteorology , geology , optics , astronomy , statistics , mathematics , quantum mechanics
Polar patch drift speed and direction have been investigated using oxygen 630 nm images recorded by an all‐sky imager at Eureka (89° CGM), Canada over an extended period, January and December 1998. Statistical studies showed that (1) the interplanetary magnetic field (IMF, from the WIND satellite) B z component linearly controls the patch speed when B z is between −7.5 nT and 0 nT. The speed tends to saturate when B z is less than −7.5nT due to nonlinear coupling between the solar wind and the magnetosphere. The average patch speed of 600 m/s is in agreement with results from earlier studies; (2) The IMF B y or the IMF clock angle has a clear control of the patch drift direction as determined by the drift azimuth angle. When ∣B y ∣ is less than 7.5nT, the drift azimuth angle is linearly and positively correlated with B y . For a large ∣B y ∣ (>7.5 nT), the positive correlation is replaced by a negative correlated linear relation and the azimuth angle tends to turn towards 180 degrees; that is, the patches drift in an antisunward direction. These IMF B y effects can be qualitatively explained by the northern winter polar ionospheric convection models developed by Weimer [1995] and Hairston and Heelis [1990]. Results from our quantitative study on the IMF control of polar patch speed and drift direction provide constraints for the development of future polar ionospheric convection models.